I. Field of the Invention
The present invention relates to the field of injection molding machines. More particularly the present invention relates to the field of injection molding machines employing a screw plasticizer and an injection plunger. Even more particularly the present invention relates to the field of injection molding machines employing a screw plasticizer, and an injection plunger adapted to high or low pressure foam molding.
II. Prior Art Statement
U.S. Pat. Nos. 2,719,326 and 2,790,203 disclose an improved pre-plasticizing units for injection molding machines. U.S. Pat. No. 3,058,161 discloses a method of molding expandable thermoplastic material of the foamable thermoplastic resinous type. U.S. Pat. No. 3,780,764 discloses a combined nozzle shut-off valve and flow control valve for use in injection molding machine nozzles. None of the above listed United States Patents disclose an automatic nozzle shut-off valve which is positively closed by an actuator.